The lawyer for a British caver has described the latest reported insults against his client by Elon Musk as "vile and false," repeating a vow to sue the tech billionaire.

The latest apparent example of erratic behavior by Musk is likely to add to concerns among investors about his leadership of Tesla, the $50 billion electric-car maker he helped found. Musk has already drawn heavy criticism for announcing plans to take the company private on Twitter and then abandoning them less than three weeks later.

Tesla(TSLA) didn't immediately respond to a request for comment Tuesday on the Buzzfeed report.

Musk initially apologized after facing a backlash over his unsubstantiated allegation. But he reignited the feud last week when he said it was "strange" that Unsworth had not sued him over the initial insult.

"Elon Musk's ongoing campaign of publishing vile and false accusations against Mr. Unsworth is inexcusable. Musk hopes to be sued and Musk deserves to be sued. He will be," L. Lin Wood, an Atlanta-based lawyer representing Unsworth, told CNN by email.

Wood told CNN last week that he was in the process of "finalizing the libel complaint" and expected to file it "in the next several days" in a Los Angeles federal court.

CNN wasn't able to independently verify the authenticity of the emails reported by Buzzfeed.

In a statement to CNN, Buzzfeed News spokesman Matt Mittenthal said the emails "confirm that those baseless claims were made by Mr. Musk himself."

Tesla chief executive Elon Musk.

Feud started over 'kid-size submarine'

The controversy began in July when Unsworth described Musk's attempt to help save the stranded boys with a "kid-size submarine" as a PR stunt, telling CNN that the miniature escape pod "had absolutely no chance of working."

He can "stick his submarine where it hurts," Unsworth said during the interview in Thailand.

Some analysts have encouraged Musk to take a break from Twitter and bring in a more disciplined second-in-command to look after day-to-day operations at Tesla.

Musk tweeted stunned investors on August 7 by tweeting that he had "funding secured" for a deal to take Tesla private, a claim that sent the company's stock haywire and reportedly sparked an investigation by the Securities and Exchange Commission. Doubts quickly surfaced about how coherent Musk's plan really was.

In the face of pushback from shareholders, he announced on August 24 that he had given up on taking the company private.

"The tweeting fiasco," Cowen analyst Jeffrey Osborne wrote to clients, "is likely to draw investor scrutiny on whether Elon's behavior, management style, and operational ability are enough to take Tesla to the next level."